Field
The present disclosure relates to an image heating apparatus, such as a fixing device mounted in an image forming apparatus including a copier and a printer employing an electrophotographic method or an electrostatic recording method, or a glossing device that improves a gloss of a toner image by reheating a fixed toner image on a recording material. Furthermore, the present disclosure relates to a heater used in the image heating apparatus.
Description of the Related Art
There is a device, serving as an image heating apparatus, including a cylindrical film, a heater that is in contact with an inner surface of the heater, and a roller that forms a nip portion together with the heater with the film in between. When small-sized sheets are continuously printed in the image forming apparatus in which the image heating apparatus is mounted, a phenomenon (a sheet non-passing portion temperature rise) in which temperature in the areas of the nip portion in a longitudinal direction where the sheets do not pass rises occurs. When the temperature of the sheet non-passing portion becomes excessively high, the parts inside the device may be damaged, and there may be cases in which, when a large-sized sheet is printed while the sheet non-passing portion temperature rise is occurring, the toner causes a high temperature offset to occur on the area of the film corresponding to the small-sized sheet non-passing portion.
As a technique of suppressing the sheet non-passing portion temperature rise from occurring, a device in which a heat generation resistor on a heater is divided into a plurality of groups (heat generating blocks) in the longitudinal direction of the heater so as to switch the heat distribution of the heater according to the size of the recording material has been proposed (Japanese Patent Laid-Open No. 2014-59508).
The sizes of the recording material used in the device are diverse and a heater that is capable of forming heat distributions that are suitable for various sheet size is in need.